1. Field of the Invention
The present invention relates to a thermoelectric conversion material for performing electron cooling or thermal power generation by energy conversion between thermal energy and electric energy, and a thermoelectric conversion element using the material. The present invention also relates to a cooling devise and an electric apparatus using the elements, and methods of converting energy using the element, such as electric power generation methods and cooling methods.
2. Description of the Related Art
Thermoelectric conversion elements are configured as follows. A plurality of p-type and n-type thermoelectric materials having positive and negative charge carriers, respectively, are joined alternately to form a certain number of junction pairs, and one type of junctions, which is, for example, pn junction along the direction of current flow, and the other type of junctions, which is np junction along the direction of current flow, are spaced apart from each other. Thermoelectric conversion elements perform cooling by passing current therethrough to cause a temperature difference between the junction regions, or perform power generation by causing a temperature difference between the junction regions to generate an electromotive force. To date, semiconductor materials such as Bi—Te, Pb—Te, and Si—Ge have been mainly researched as thermoelectric conversion materials, and some materials have been put to practical use in certain fields.
Nevertheless, property of the materials has not yet been satisfactory to attain full-fledged commercialization for general consumer products, and improvement in property of thermoelectric conversion materials has been demanded. Recently, among oxide materials, which were conventionally considered as unsuitable for thermoelectric materials, substances that exhibit high thermoelectric conversion performance, such as NayCoO2 (y=0.2 to 1) having a layered bronze structure, have been found (see JP 09(1997)-321346A). The thermoelectric conversion performance of this system compares with that of Bi—Te, which is a practically usable thermoelectric semiconductor material, and it is highly expected that thermoelectric power generation will be realized with an oxide material that is stable even in an oxidizing atmosphere.
However, since NayCoO2 tends to be adversely affected by humidity in air, a problem has been to achieve high thermoelectric performance in a normal air atmosphere.
It is an object of the present invention to provide an oxide material that has high thermoelectric conversion performance and is stable in an oxidizing atmosphere as well as in an air atmosphere.